1. Field of the Invention
The present invention relates generally to crash test dummies and, more particularly, to a string pot system for a crash test dummy.
2. Description of the Related Art
Automotive, aviation, and other vehicle manufacturers conduct a wide variety of collision testing to measure the effects of a collision on a vehicle and its occupants. Through collision testing, a vehicle manufacturer gains valuable information that can be used to improve the vehicle, authorities examine vehicles to submit type approval, and consumer organizations provide information on vehicle safety ratings to the public.
Collision testing often involves the use of anthropomorphic test devices, better known as “crash test dummies”, to estimate a human's injury risk. The dummy must possess the general mechanical properties, dimensions, masses, joints, and joint stiffness of the humans of interest. In addition, they must possess sufficient mechanical impact response similitude and sensitivity to cause them to interact with the vehicle's interior in a human-like manner.
The crash test dummy typically includes a head assembly, spine assembly (including neck), rib cage assembly, abdomen, pelvis assembly, right and left arm assemblies, and right and left leg assemblies. Generally, the arm assembly has an upper arm assembly and a lower arm assembly. The upper arm assembly is typically connected to a shoulder assembly, which, in turn, is typically connected to the spine assembly.
Current string pots use a spring to maintain tension on a string which is wound up by a pulley inside the body of the crash test dummy. A potentiometer or encoder measures the position of the pulley. This can be calibrated to measure displacement. When used in the crash test dummy, the spring is unable to maintain tension on the string while accelerating the pulley during high string accelerations. When larger springs are used, they can accelerate at higher rates, but then apply an unacceptable load to the rib or other part which is being measured. As a result, there is a need in the art to provide a system that maintains spring tension with a motor and/or flywheel and an active control system that maintains a constant tension on the string even with high acceleration rates. Thus, there is a need in the art for a string pot system for a crash test dummy that meets at least one of these needs.